Though children may not be impressed with the logic, watering your lawn in the middle of the day, when it's windier and temperatures are higher, results in more evaporation.

Tips for keeping your lawn healthy

From eNews, July 20, 2006

It doesn't take a scientist to tell you your lawn has been
suffering through the hot, dry weather prevalent in Minnesota
during the past nine weeks.

But it might take one to tell you what lawn care advice to
follow.

A labyrinth of information exists on the Internet, including
recipes for remedies and tonics that allegedly help grass during
dry spells: Water your lawn sparingly. Don't water your lawn at
all. Pour a concoction that includes beer, pop, and mouthwash on
your lawn.

When rainfall doesn't seem to be forthcoming, one of the best
ways to rescue your lawn is through timely, appropriate watering,
says Bob Mugaas, a horticulturist with the University of Minnesota
Extension Service.

For a green, actively growing lawn, Mugaas recommends applying
about 1 to 1.5 inches of water on your lawn every 7 to 10 days.
Where some loss of green color can be tolerated, he suggests
applying at least one-half to three-quarters of an inch of water
every 7 to 10 days.

He adds that as a general guideline, during hot and windy
conditions, intervals between waterings should be shorter due to an
increased rate of drying.

"Lawn grasses will let you know when they are getting thirsty,"
Mugaas says. "When you start seeing areas of a dark, bluish-gray
color in your lawn, that's a good indicator that the lawn is
beginning to dry out, and some additional water will help ease that
stress."

According to Mugaas, Minnesota grass plants have relatively good
tolerance to hot and dry periods, especially where they have been
conditioned properly. But there are limits to that tolerance,
especially with many of the contemporary bluegrass and perennial
ryegrass varieties that have been introduced over the last several
decades.

If the plant gets too hot and/or dry internally, tissue damage
can occur and the plant usually dies, according to Mugaas. That's
why it's not a good idea to let lawns go dormant or completely dry
and brown for extended periods of time.

Owners of automated lawn watering systems can increase the
amount of time water is applied and increase the time periods
between waterings, Mugaas says. This can help accommodate community
water restrictions such as odd-even or address-based watering
schedules.

He also recommends applying water early in the day. Normally,
winds aren't high and temperatures are cooler, allowing for maximum
absorption. Watering in the middle of the day, when it's windier
and temperatures are higher, results in more evaporation.

Lastly, Mugaas says to minimize traffic on lawns during
extremely dry conditions. Avoiding hard play and heavy traffic will
help prevent your grass from permanent injury.